Garlic, also known as Allium sativum, is a species in the onion genus, which has been commonly used worldwide as a culinary herb or nutraceutical foodstuff. There have been numerous medical properties ascribed to garlic for the treatment or prevention of various metabolic disorders or infections. It has also been used in folk medicine for thousands of years.
Garlic, in its fresh or crushed form, contains various types of derivatives, which includes the sulphur-containing compounds that contribute to its distinctive smell and taste, and non sulphur-containing compounds. Allicin is thought to be one of the major chemical compounds of garlic that is responsible for much of the odour and biological activity of garlic. Allicin is a chemically unstable, colourless to straw-coloured oil, converted from its precursor alliin [(+)(S-allyl-L-cycteine sulfoxide)] by the enzyme alliinase. An intact garlic clove does not contain allicin but rather its odourless precursor alliin. As alliin and alliinase are found in different compartments of the garlic clove, allicin is only converted into allicin when the cutting or crushing of the clove releases the alliinase and allows it to come into contact with alliin. Allicin is both unstable and volatile, and would naturally be converted to approximately 15 different metabolites depending on the media in which it is converted. These metabolites include diallyl disulphide, diallyl trisulphide, vinyl dithiins, ajoene and others. A method for preparing allicin in high yield and volume is described in EP 1404853 A1, part of the contents of which are herein incorporated by reference.
Ajoene is among one of the important garlic metabolites that is presently of interest in a number of fields of endeavour, including both human and animal pharmaceuticals. It has been documented in the art that ajoene possesses a wide range of medicinal properties, including antioxidants, antithrombotic, broad-spectrum antimicrobial, prevention of yeast infection, and inhibition of gene-controlling quorum sensing activities. However, the study and hence the use of ajoene for such purposes has been curtailed since the existing methods available for producing ajoene have low selectivity for ajoene. Consequently, ajoene is expensive to produce and only in relatively low yields.
There have been a few existing technologies described in the prior art related to the process for producing ajoene. For example, U.S. Pat. No. 5,612,077(A) describes a method to produce a macerate containing mainly Z-ajoene using edible oil, but in small volumes and low concentration. Another U.S. Pat. No. 5,741,932(A) describes a method of preparing ajoene using cyclodextrin, which is a complicated multi-step method and yet it produces small volumes of ajoene at a low concentration. Other approaches to ajoene production from allicin, such as that described in PCT publication No. WO/2010/100486 and Block et al. Am Chem. Soc., 1986, 108 (22), have required the use of large volumes of volatile hydrocarbon solvents that may not be suitable to be used in production of food or herbal extracts. The solvent extraction approach of ajoene is also labour-intensive and costly.
In view of the various medicinal or therapeutic benefits of ajoene and ajoene-containing composition, it is desirable for the industry to provide an improved and innovative process for producing ajoene to overcome the drawbacks of the existing technologies.